Insufflatory surgery involves filling a body cavity with pressurized gas to maintain the cavity under a certain predetermined pressure. Such surgery may be performed by first puncturing the skin of a desired body cavity region with a needle. Insufflation gas is then introduced into the body cavity to inflate the cavity via a stylet in the needle.
A trocar is then used to puncture the body cavity. The trocar is inserted through a cannula or sheath, which cannula partially enters the body cavity through the incision made by the trocar. The trocar may then be removed from the cannula, and an elongated endoscope may be inserted through the cannula to view the anatomical cavity.
Various types of cannula or trocar assemblies are provided with valves so that when the trocar or other surgical instrument is removed from or inserted into the cannula a relatively constant or certain pressure is maintained within the body cavity.
For example, U.S. Pat. Nos. 4,601,710 to Moll and 4,654,030 to Moll et al. disclose trocar assemblies which include an elongate trocar obturator having a piercing tip at its front end and an elongate trocar tube or cannula in which the trocar obturator is housed. As shown in the '030 patent, a flapper valve may be employed to close off the cannula passage after the trocar obturator or other instrument has been withdrawn.
A gasket may also be employed to ensure a seal between the trocar assembly and an instrument inserted therein. U.S. Pat. No. 4,000,739 to Stevens, for example, teaches a hemostasis cannula having a pair of juxtaposed gaskets mounted in the passageway to the cannula, the first having a round hole and the second a Y-shaped slit. U.S. Pat. No. 3,994,287 to Turp et al. describes a trocar assembly which includes a flexible insulating ring received in a flange and a collar which retains the flexible ring in the flange. The flexible ring is allowed to flex as an instrument is inserted into the cannula and provides a seal with the instrument to prevent gas leakage.
Endoscopic surgical procedures employ a variety of surgical instruments, e.g., endoscopes, biopsy forceps, bipolar forceps, coagulation probes, etc. Due to the relatively noninvasive nature of endoscopic procedures, endoscopy is a preferred surgical approach when possible. As such, additional instruments and accessories for use in endoscopic procedures are being introduced at a rapid pace. These instruments have differing sizes, for example, some instruments have a cross-sectional diameter in their elongate regions on the order of 5 mm whereas others have a diameter of 10 mm or larger. In recognition of this instrument variability, cannulas are available in different inner diameters. Commercially available trocars offer cannulas having a broad range of inner diameters, ranging from 3 to 12 mms (e.g., 3, 5, 7, 8, 10, 11 and 12 mm sizes).
Despite the availability of trocar assemblies having cannulas of various sizes, it is both inconvenient and impractical for a surgeon to insert multiple cannulas into a patient to accommodate the various instrument sizes employed in a given surgical procedure. This greatly restricts the flexibility available to surgeons in performing endoscopic procedures. For example, the use of a 5 mm instrument in a 10 mm cannula is not possible because a gas seal would not exist between the trocar assembly and the instrument. Similarly, the use of a 10 mm instrument in a 5 mm cannula is impossible because the instrument simply doesn't fit. It has therefore been necessary heretofore for a surgeon to effect multiple cannula placements or to employ accessory devices having a predetermined aperture diameter to accommodate the use of instruments of varying sizes. Consequently, such multiple placement dictates multiple invasionary punctures into the body of a patient and the use of accessory devices can be a clinical nuisance. It is desirable to decrease the number of punctures because, e.g., the possibility of infection would be decreased, patient discomfort would be decreased and both time and money would be saved, while accommodating instruments of varying diameters.